Snowfall is an important precipitation system in Beijing. In this study, observation data in combination with the WRF mesoscale numerical simulation model were used to analyze the microphysical processes of two different snowfall cases in the northern mountain area of Beijing. The results showed the following: (1) Because of the great differences in weather situation and water vapor transport during these two snowfall processes, great differences existed in the microphysical mechanism of these two snowfall cases. In period I of November 5, 2015, due to a strong water vapor transport, there was more liquid water in the cloud, and deposition and rimming processes were the main formation processes for snow particles. However, deposition and coalescence were the main formation processes for snowfall cases on January 24 and in period II of November 5-6 for the weak water vapor transport. (2) In period I of November 5, the air contained ice crystal (9%), snow crystal (72%), cloud liquid water (6%), and rainwater (12%), and the snow particles grew with deposition (78%) and rimming (20%) processes. On January 24, the air contained ice crystal (28%) and snow crystal (72%); meanwhile, period II of November 5-6 had a similar portion: ice crystal (11%) and snow crystal (88%). Moreover, snow particles grew through deposition and coalescence on January 24 and in period II of November 5-6. (3) Updraft has a great influence on the ice crystal and snow crystal growth processes because it results in sufficient water vapor. The vertical motion and water vapor make more snow for strong deposition, rimming, and coalescence processes.